One of the features of the Carriage trailers is that they don't need slide awnings... The slides also have rubber roofs and they slant.. On the trailer side they have large "squeegees" on the top and sides that clean anything off as you are closing the slides... I cover all rubber with 303 Aerospace Protectant so there are no worries about dry rot...
I leave the slides out all the time and "exercise" them from time to time by pulling them in for awhile and then pushing them back out... I have had no problems with anything this way....
Ken....